0.1.1

Fix concurrency and parsing edge cases for 0.1.1

- Parser toggles fence mode on every line (before header parsing) and
  respects ~~~ fences, so code blocks anywhere in a file are never
  parsed as quiz content
- Failed quiz-view opens remove their config by identity, not array index
- Settings writes serialize through a persistence queue
- Vault scan uses bounded concurrency (8 workers) for cachedRead
- Release workflow packages assets from the tag checkout; versions.json
  is committed to main only after the release is published
- Manifest and package version bumped to 0.1.1